Certain separation materials can be used for separating plasma from whole blood. One example of such a separation material is an asymmetric separation membrane, which can be used to separate solid or semi-solid components from liquid components through the principle of size exclusion. For plasma separation, the asymmetric separation membrane traps formed blood components such as red and white blood cells in the larger pores at the top of the separation material and allows plasma to filter through the smaller pores at the bottom of the separation material.
The filtered plasma can then be used for other purposes such as but not limited to analyte measurement. For assay uses, plasma separation membranes have been used commercially for large molecule assays for certain proteins and lipids. Examples include assays directed at cardiac biomarkers such as Troponin I, albumin, cholesterol, etc. Most of the current applications of plasma separation membranes are in lateral flow assays, where the separation material is mounted on top of another absorbent material which houses the assay reagents and where the reaction happens. This limits the use of this separation membrane to a limited set of assays which use mostly undiluted plasma and which can be performed on a surface.
Unfortunately, these conventional plasma separation membranes are configured in manner that can negatively interfere with plasma sample integrity, particularly when the plasma is used for certain assays. For example, a hemolysis preventing agent typically used with such separation membranes is a substance that can leach out of the separation membrane surface and into the collected plasma sample, which can then result in erroneous measurements for certain assays. Although the anti-hemolytic effect is generally desirable for sample integrity, errors associated with such coatings is not desirable.